1. Field of the Invention
The present invention generally relates to devices for automatically answering telephone calls such as facsimile machines, modems, answering machines, and the like, and more particularly relates to a device for detecting the connection status of an extension phone connected to one of such automatic telephone call answering devices.
2. Description of Related Art
A variety of devices have been developed for automatically answering incoming telephone calls received from a public switched telephone network (PSTN) and for automatically recording messages or data received in the incoming telephone call. Examples include conventional facsimile machines, data modems, answering machines and the like. Recently, integrated devices have been developed which provide for all of the above functions. Once such device is a data/fax/voice modem, which is typically employed in connection with a host computer. The data/fax/voice modem automatically answers an incoming telephone call received along a telephone line connected to the PSTN. The data/fax/voice modem then determines whether the received telephone call includes a data message, a facsimile message, or an ordinary voice message. If the incoming message is a data message, a data modem module of the data/fax/voice modem operates to receive and decode the data message for storage in a computer memory of the host computer, typically within a hard disk drive memory device. If the incoming message is a facsimile message, a fax module of the data/fax/voice modem operates to receive and decode the facsimile image for storage within the memory of the host computer. Alternatively, a facsimile print-out device may be connected to the data/fax/voice modem for automatically printing the facsimile image, thus eliminating the need to store the facsimile image within the host computer. If the incoming message is a voice message, an answering machine module of the data/fax/voice modem operates to answer the incoming voice communication. In particular, the answering machine module of the data/fax/voice modem initially outputs a prerecorded greeting then records a voice message in response to the greeting. Digital-to-analog converter means may be included within the data/fax/voice modem for converting the incoming voice message to digital signals for storing in the memory of the host computer. Alternatively, the data/fax/voice modem may be connected to a conventional analog recording device such as a tape recorder for recording the voice message. As can be appreciated, a variety of implementations and configurations are available.
Although the data/fax/voice modem provides a convenient tool for answering incoming telephone calls and storing data, fax or voice messages accordingly, a problem can occur when an operator attempts to manually answer the incoming telephone call using an extension line after operation of the data/fax/voice modem has commenced. In particular, if the incoming message is a voice message, an operator may wish to override the automatic answering machine operation of the data/fax/voice modem and answer the telephone call directly. However, with typical data/fax/voice modems, once the modem has answered the telephone call and begins recording a message in response thereto, the answering machine operation of the modem cannot be conveniently terminated. Usually, termination requires manually deactivating the modem by pressing appropriate buttons on the modem itself or by entering commands into the host computer. At best, the need to manually deactivate the data/fax/voice modem is inconvenient. However, where the modem or host computer is remote from the location of the operator, it may be difficult, or at least highly frustrating, for the operator to manually deactivate the modem.
This problem, although described with reference to a data/fax/voice modem, can occur in any circumstance where a device automatically answers an incoming telephone call. In such circumstances, it would be desirable to allow an operator to disable the modem or other telephone answering device, by merely picking up the telephone call through the extension line. Hence, it would be desirable to provide a mechanism for detecting the off-hook status of an extension line for possible use in controlling operation of the modem or other telephone answering device.